Hello and welcome to this site dedicated to arachnology or the study of arachnids. We wanted to create a website that brings together the most important information about this fascinating science. We can’t find another website that thoroughly explores the topic, so we decided to change that by creating this one. We are very excited to undertake this task and to respond to all questions you might have about this science. You might be visiting our page because you have a pet spider or simply because you’re curious as to what these creatures are like. We aim to make this website as accessible as possible by explaining everything in a simple and entertaining way.

As you can guess, we are spider enthusiasts and we get a lot of questions about our pet spiders, so we decided to combine our knowledge into this joint project.

We hope you find the information on arachnology useful and we also hope you find the content of this website is thorough and exhaustive. Enjoy learning about these curious little creatures with us!

Arachnology – Etymology of the Word

Let us first start with the basic concepts. The name of the science arachnology comes from the Greek word arachne, meaning spider and the logia, meaning the study of a certain subject. The word arachne itself comes from the mythological heroine Arachne who was turned into a spider as a punishment for her pride as she challenged the goddess Athena to a weaving contest.

However, what you might not know is that arachnology is not just the study of spiders; the word is a false friend.

Arachnids

Arachnology is in fact the study of various subgroups, the three main ones being:

• Araneology – the study of spiders
• Acarology – the study of mites and ticks
• Scorpiology – the study of scorpions

What they have in common is that they are all arachnids. Arachnids are a class of joint-legged invertebrate animals from the family of Chelicerata. There are approximately 100,000 distinctive species of arachnids, half of which are spiders.

Here are all the orders of the arachnid family, some of which are extinct today:

• Araneae – spiders
• Solifugae – camel spiders
• Ricinulei – hooded tickspiders
• Amblypygi – whip spiders
• Opiliones – harvestmen
• Acariformes – mites
• Parasitiformes – mites and ticks
• Scorpiones – scorpions
• Schizomida – short-tailed whipscorpions
• Palpigradi – micro-whipscorpions
• Pseudoscorpiones – pseudoscorpions
• Thelyphonida – vinegaroons
• Xiphosura – horseshoe crabs
• Phalangiotarbi (extinct)
• Uraraneida (extinct)
• Haptopoda (extinct)
• Trigonotarbida (extinct)

Arachnids usually have eight legs, but they are not always regular limbs used for walking or climbing; some have sensory functions, while others are appendages that only look like legs.

The number of legs is what distinguishes them from insects, which always have six legs. It’s not impossible, but it’s highly uncommon for arachnids to have fewer than eight legs once they reach adulthood (larvae don’t always have eight legs). Another way to distinguish an arachnid from an insect is that the former species do not have wings or antennae.

The legs of the arachnids serve distinctive purposes. The first pair of legs, called the chelicerae, are used for defence and feeding. The second pair, known as the pedipalps, are also used for feeding, as well as locomotion, and reproduction.

Furthermore, the body of the arachnids is divided into subsections. To begin with, arachnids are made out of two tagmata – the prosoma (or the cephalothorax) and the opisthosoma (or the abdomen). Depending on the specific type of arachnid, it might be hard to tell (for an amateur arachnologist) where the abdomen stars since some species have fused in together parts (the acari is a good example).

Lastly, all arachnids have an exoskeleton. They also sport cartilage-like tissue, called the endosternite.

In the following sections, we will take a look at a few orders of arachnids that we believe are the most interesting.

Araneae

The Araneae order (from Latin, “spider”) can be divided into 129 families with over 49,000 species. Spiders are some of the most diverse animal species. They can be found on every continent, except for Antarctica.

It’s estimated that the first primitive spiders appeared in the Devonian period more than 386 million years ago, while their modern counterparts emerged in the Carboniferous period about 300 million years ago.

Spiders always have eight legs, as well as fangs that can inject venom and spinnerets that can produce silk to create webs. They also have a centralised nervous system, one of the most complex ones in the arachnid family.

A curious fact about them, that distinguishes them from other arachnids, is that they don’t have extensor muscles on their limbs, but they rather extend them through hydraulic pressure.

Almost all spiders are predators and they are thought to capture between 400-800 million tons of prey every year, that are mostly insects, but sometimes even birds and lizards. Spiders use different ways to capture prey. They either trap prey in their webs, they can lasso it, or they exhaust it and then capture it.

Spiders also use various techniques to detect prey. Some sense locomotive vibrations, while others use their vision. The more intelligent spider species may change their hunting techniques. Spiders cannot digest the prey as it is, so they instead turn it into a liquid by showering it with their digestive enzymes while it’s in the web.

In terms of social behaviour, there are spider species that live solitary, but may tolerate others. In addition to that, there are spiders that live in colonies and share their prey. Some spider-mothers also take care of their young.

The life span of a spider is generally a few years (mostly two or three), but tarantulas can live up to 20-something and the oldest one, called Number 16, lived to be 28 years old. As with other animals, spiders in captivity live longer lives.

Opiliones

The Opiliones order (from Latin, “shepherds”) is the order of the harvestmen or the daddy longlegs. They are called harvestmen because they appear in autumn in time for the harvest, and daddy longlegs, because… their legs are long! There are approximately 6,000 species of harvestmen, but there could be more. Harvestmen can be found anywhere but Antarctica.

We wanted to include harvestmen, because they are often mistaken for spiders, but they are two distinctive species. They are not close related either. Harvestmen can be most easily distinguished by their body, which has fused in together parts, unlike that of spiders. Another distinctive feature are their two eyes.

Another interesting fact is that harvestmen do not have venom glands like spiders, so they pose no threat to humans. While spiders are famous for their web-weaving, harvestmen don’t produce silk, so they don’t create webs.

Interestingly, harvestmen are a little bit older than spiders, having first emerged 400 million years ago. What’s more, they haven’t changed that much since then.

Although harvestmen are often referred as daddy longlegs, some species have short legs. One pair of legs serves as antennae. The harvestmen body is very strong and some species even develop a dorsal shield for protection.

Harvestmen are usually omnivores that feed with insects, eggs, and plants. Curiously, they are also known as scavengers, so they will eat dead plants and animals, as well as animal excrements. Talking about a diverse diet! What makes them stand apart from almost all other arachnids is that they can consume solid food.

Another interesting thing about harvestmen is that they mate directly. The male can even entice the female to mate again after the first act. Males later guard the eggs, even the ones resulting from other mates of the female.

Harvestmen generally live for about a year.

Acariformes

The Acariformes order includes over 32,000 species in 351 families, although they are probably hundreds of thousands non-described species. The Acariformes are simply put – mites. They can be divided into two big groups – Sarcoptiformes and Trombidiformes.

The first group, the Sarcoptiformes, can digest solid foods, just like harvestmen. They can be classified as herbivores, although some also feed on fungi and detritus. Some Acariformes can be described as plant parasites that cause a great deal of damage like the Eriophyidae and the spider mites.

There are also animal parasites among them and they live in herbivore hosts like cattle and sheep. The Chorioptes, a type of Acariformes, often attach themselves to pandas, which is thought to be a risk to conservation efforts.

Parasitiformes

The Parasitiformes were mistakenly considered a type of Acariformes, but they are two distinctive types of arachnids. There are approximately 130 families of Parasitiformes and the number of the species can be placed between 100 and 200 thousand. Parasitiformes likely emerged in the Paleozoic Era between 541 and 251 million years ago.

The Parasitiformes can be divided into four big groups: Holothyrida (predatory mites), Ixodida (ticks), Mesostigmata (predatory and parasitic mites), and Opilioacarida (mites resembling harvestmen in appearance).

The Parasitiformes can be distinguished by their lack of body segmentation. Their fused in body parts, including torso, eyes, legs, and organs, are known as the opisthosoma. The Parasitiformes vary in size with the smallest members being less than 0.5 mm long, while the biggest are generally about 2 to 3 mm.

The Parasitiformes mate indirectly with the male putting a spermatophore in the female’s genital opening. Then, the female lays eggs from which larvae hatch. The larvae experience a few moults before it turns into an adult.

These species have a very diverse diet. Some feed on the blood of their host, others feed on carcasses, excrements, hair, skin, feathers, and dust, and sometimes even on alive insects.

Scorpiones

The Scorpiones orders includes over 2,500 species spread over 22 families. Scorpions likely emerged 435 million years ago in the Silurian Era. There are many scorpion fossils found throughout the years, and we know that scorpions used to be both terrestrial and aquatic.

What defines a scorpion is its exoskeleton, eight legs, grasping pincers, and a tail that always features a stinger. The stinger is used for both offence and defence. It can be used to paralyse or kill prey or predators who try to hurt the scorpion itself.

The stinger is also used in the mating ritual. The male and female scorpions dance before mating, a process that can take hours, during which the male may sting the female to subdue her. They are also known to “kiss” by touching their mouth parts. And they said romance is dead.

What’s interesting about scorpions is that they give live birth and the mother takes care of her offspring until the baby scorpions can hunt on their own.

Scorpions usually hunt insects like grasshoppers, beetles and wasps, but some species are known to have preyed on vertebrates such as lizards, snakes and even mammals. Generally, scorpions are opportunistic as in they’d choose the prey that best suits their present situation.

Scorpions are feared by humans, but apparently only 25 species produce venom that can kill a person. The most lethal scorpion bite is that of the Indian Red Scorpion. Victims might feel nauseous and at worst accumulate fluid in their lungs.

You should be wary of scorpions and avoid direct contact, so they don’t see you as a danger. The general rule of thumb is that scorpions with larger pincers and thinner tails are only mildly venomous.

Pseudoscorpiones

The Pseudoscorpiones order includes more than 3,000 species, although new ones are continuously being discovered. The first member of the Pseudoscorpiones order dates back to the Devonian period, about 383 million years ago and it looks much like the contemporary pseudoscorpions.

Pseudoscorpions usually inhabit tropical and subtropical regions, but they can be found in cold climates as well. Although they look a lot like their arachnid cousins the scorpions, they pose no threat to humans. What’s more, they are actually beneficial to humanity since they prey on moth larvae, booklice, ants and mites. They look out for us!

Pseudoscorpions are very small in size (0.2-0.8 mm) and many people can’t even see them with a naked eye. If they seem them, however, many assume that they are small spiders or mites. Pseudoscorpions have eight legs and between five to seven segments. They also have pincer-like pedipalps like scorpions.

Similar to scorpions, pseudoscorpions also have a mating dance during which the male tries to put the female on top of the spermatophore he placed earlier. Once the baby pseudoscorpions hatch, they ride on the mother’s body for a while. Interestingly, the adults exhibit the same behaviour as they sometimes ride on other animals.

Arachnology

It’s really difficult to pin point when the science of arachnology developed. Scientists have studied arachnids for centuries, but it wasn’t until the 19th century when some scholars decided to specialise in arachnology. Still, it took some time for the science to truly develop.

The American Arachnological Society notes that there were only a couple of arachnologists even in the early 20th century. However, the work of tireless individuals who were exploring this fascinating scientific niche paid off and now the term arachnology is not only something you can hear at a fancy cocktail party.

Arachnologists are tasked with classifying arachnids, which is a lot of work since new species are continuously being discovered.

Once they find such new species, arachnologists study their biology and try to determine their evolutionary cycle and their closeness with other arachnid species. Later, the new species are being observed to note how they behave in groups and in their respective environments.

Other arachnologists study already known species to find out more information about their autonomy and behaviour. For instance, spiders are now being studied to determine whether their silk production can be used on a massive level.

It’s also really important to study venomous spiders and scorpions in order to know how to help people and animals who have been bitten or stung by a venomous arachnid. There are now even attempts to utilise arachnid venom to use it in small quantities as a medicine, and we are very excited for that possibility.

Arachnological Societies

If you found this website to be interesting and you now want to follow various arachnological organisations and their valuable work for the field of arachnology and for the preservation of arachnids, we want to give you this short list of arachnological societies around the world:

• The American Arachnological Society
• The International Society of Arachnology
• The British Arachnological Society
• The African Arachnological Society
• Die Arachnologische Gesellschaft
• The Australasian Arachnological Society
• The Czech Arachnological Society
• The European Society of Arachnology

Thank You

We want to finish this overview of arachnology with a heartfelt thank you. Thank you for supporting our venture by visiting our website and reading our content. We hope we were able to answer the most common questions regarding arachnids and arachnology.

We also hope that we were able to make you appreciate these little creatures and their complex nature. Thank you and till next time!